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/*! \file
  \brief Epilogue for threadblock scoped GEMMs using Tensor Ops.

  The epilogue rearranges the result of a matrix product through shared memory to match canonical
  tensor layouts in global memory. Epilogues support conversion and reduction operations.

*/
#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/numeric_types.h"
#include "cutlass/array.h"

#include "cutlass/platform/platform.h"

#include "cutlass/gemm/gemm.h"

#include "cutlass/transform/threadblock/regular_tile_iterator_pitch_linear.h"

#include "cutlass/epilogue/warp/fragment_iterator_tensor_op.h"
#include "cutlass/epilogue/warp/fragment_iterator_complex_tensor_op.h"
#include "cutlass/epilogue/warp/tile_iterator_tensor_op.h"
#include "cutlass/epilogue/warp/tile_iterator_tensor_op_mixed.h"
#include "cutlass/epilogue/threadblock/default_thread_map_tensor_op.h"
#include "cutlass/epilogue/threadblock/predicated_tile_iterator.h"
#include "cutlass/epilogue/threadblock/shared_load_iterator.h"
#include "cutlass/epilogue/threadblock/shared_load_iterator_mixed.h"

#include "cutlass/contrib/epilogue/threadblock/epilogue.h"
#include "cutlass/contrib/epilogue/threadblock/predicated_tile_iterator.h"

////////////////////////////////////////////////////////////////////////////////

namespace cutlass {
namespace contrib {
namespace epilogue {
namespace threadblock {

////////////////////////////////////////////////////////////////////////////////

namespace detail {

template <typename ElementOutput, typename ElementAccumulator, int ElementsPerAccess,
          typename ThreadblockShape, typename WarpShape, typename InstructionShape,
          typename ThreadMap>
struct DefaultIteratorsTensorOp {
  using WarpTileIterator =
      cutlass::epilogue::warp::TileIteratorTensorOp<WarpShape, InstructionShape,
                                                    ElementAccumulator, layout::RowMajor>;

  using SharedLoadIterator =
      cutlass::epilogue::threadblock::SharedLoadIterator<ThreadMap, ElementAccumulator>;

  static int const kFragmentsPerIteration = 1;
};

/// Partial specialization for float <= float x 4
template <typename ThreadblockShape, typename WarpShape, typename InstructionShape,
          typename ThreadMap>
struct DefaultIteratorsTensorOp<float, float, 4, ThreadblockShape, WarpShape, InstructionShape,
                                ThreadMap> {
  using WarpTileIterator =
      cutlass::epilogue::warp::TileIteratorTensorOp<WarpShape, InstructionShape, float,
                                                    layout::RowMajor>;

  using SharedLoadIterator = cutlass::epilogue::threadblock::SharedLoadIterator<ThreadMap, float>;

  static int const kFragmentsPerIteration = 2;
};

/// Partial specialization for half <= float x 8 epilogues avoids shared memory bank conflicts.
template <typename ThreadblockShape, typename WarpShape, typename InstructionShape,
          typename ThreadMap>
struct DefaultIteratorsTensorOp<half_t, float, 8, ThreadblockShape, WarpShape, InstructionShape,
                                ThreadMap> {
  using WarpTileIterator =
      cutlass::epilogue::warp::TileIteratorTensorOpMixed<WarpShape, InstructionShape, float, 32,
                                                         16, 8, 8>;

  using SharedLoadIterator =
      cutlass::epilogue::threadblock::SharedLoadIteratorMixed<ThreadMap, float, 32, 16, 8, 8>;

  static int const kFragmentsPerIteration = 2;
};
}  // namespace detail

////////////////////////////////////////////////////////////////////////////////

/// Defines sensible defaults for epilogues for TensorOps.
template <typename Shape_, typename WarpMmaTensorOp_, int PartitionsK, typename OutputOp_,
          int ElementsPerAccess>
struct DefaultEpilogueTensorOp {
  using Shape = Shape_;
  using WarpMmaTensorOp = WarpMmaTensorOp_;
  static int const kPartitionsK = PartitionsK;
  using OutputOp = OutputOp_;
  static int const kElementsPerAccess = ElementsPerAccess;

  using ElementOutput = typename OutputOp::ElementOutput;
  using LayoutC = typename WarpMmaTensorOp::LayoutC;
  using ElementAccumulator = typename WarpMmaTensorOp::ElementC;

  //
  // Thread map
  //

  using OutputTileThreadMap = typename cutlass::epilogue::threadblock::DefaultThreadMapTensorOp<
      Shape, typename WarpMmaTensorOp::Shape, kPartitionsK, ElementOutput,
      kElementsPerAccess>::Type;

  static bool const UseCUDAStore = platform::is_same<ElementOutput, double>::value;

  using OutputTileIterator =
      cutlass::contrib::epilogue::threadblock::PredicatedTileIterator<OutputTileThreadMap,
                                                                      ElementOutput, UseCUDAStore>;

  using AccumulatorFragmentIterator = typename std::conditional<
      is_complex<ElementOutput>::value,
      cutlass::epilogue::warp::FragmentIteratorComplexTensorOp<
          typename WarpMmaTensorOp::Shape, typename WarpMmaTensorOp::Policy::Operator::Shape,
          typename WarpMmaTensorOp::Policy::Operator::ElementC,
          typename WarpMmaTensorOp::Policy::Operator::FragmentC, LayoutC>,
      cutlass::epilogue::warp::FragmentIteratorTensorOp<
          typename WarpMmaTensorOp::Shape, typename WarpMmaTensorOp::Policy::Operator::Shape,
          typename WarpMmaTensorOp::Policy::Operator::ElementC,
          typename WarpMmaTensorOp::Policy::Operator::FragmentC, LayoutC>>::type;

  /// Support several implementations depending on structure of epilogue
  using DefaultIterators =
      detail::DefaultIteratorsTensorOp<ElementOutput, ElementAccumulator, kElementsPerAccess,
                                       Shape, typename WarpMmaTensorOp::Shape,
                                       typename WarpMmaTensorOp::Policy::Operator::Shape,
                                       typename OutputTileThreadMap::CompactedThreadMap>;

  using WarpTileIterator = typename DefaultIterators::WarpTileIterator;
  using SharedLoadIterator = typename DefaultIterators::SharedLoadIterator;

  /// Hard-coded padding elements added
  using Padding = cutlass::MatrixShape<0, 64 / sizeof_bits<ElementAccumulator>::value * 4>;

  static int const kFragmentsPerIteration =
      (kPartitionsK == 1 ? DefaultIterators::kFragmentsPerIteration : 1);

  //
  // Define the epilogue
  //
  using Epilogue = cutlass::contrib::epilogue::threadblock::Epilogue<
      Shape, WarpMmaTensorOp, kPartitionsK, OutputTileIterator, AccumulatorFragmentIterator,
      WarpTileIterator, SharedLoadIterator, OutputOp, Padding, kFragmentsPerIteration>;
};

}  // namespace threadblock
}  // namespace epilogue
}  // namespace contrib
}  // namespace cutlass

////////////////////////////////////////////////////////////////////////////////
